Phenylcarbazole-based compound and organic electroluminescent device employing the same

ABSTRACT

A phenylcarbazole-based compound is represented by Formula 1, and has superior electric properties and charge transport abilities, and thus is useful as a hole injection material, a hole transport material, and/or an emitting material which is suitable for fluorescent and phosphorescent devices of all colors, including red, green, blue, and white colors. The phenylcarbazole-based compound is synthesized by reacting carbazole with diamine. The organic electroluminescent device manufactured using the phenylcarbazole-based compound has high efficiency, low voltage, high luminance, and a long lifespan.

CROSS-REFERENCE TO RELATED PATENT APPLICATION AND CLAIM OF PRIORITY

This application claims the benefit of Korean Patent Application No.10-2004-0098747, filed on Nov. 29, 2004, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference. This application is a Continuation-in-Part ofapplication Ser. No. 11/286,421 filed on the 25 Nov. 2005, and assignedto the assignee of the present invention. All benefits accruing under 35U.S.C. §120 from the present application are also hereby claimed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a phenylcarbazole-based compound and anorganic electroluminescent device employing the same, and moreparticularly, to a phenylcarbazole-based compound which has electricstability, superior charge transport ability and high glass transitiontemperature and can prevent crystallization, and an organicelectroluminescent device using an organic layer including the same.

2. Description of the Related Art

An electroluminescent (EL) device is a self-emission type display deviceand has received significant attention owing to its merits of a wideviewing angle, superior contrast, and rapid response. EL devices aredivided into inorganic EL devices in which an emitting layer is composedof an inorganic compound, and organic EL devices in which an emittinglayer is composed of an organic compound. An organic EL device hassuperior luminance, driving voltage, and response rate to an inorganicEL device and can display multicolors, and thus much research intoorganic EL devices has been conducted.

The organic EL device generally has a layered structure of anode/organicemitting layer/cathode. When a hole transport layer and/or an electroninjection layer is further interposed between the anode and the emittinglayer or between the emitting layer and the cathode, an anode/holetransport layer/organic emitting layer/cathode structure or ananode/hole transport layer/organic emitting layer/electron injectionlayer/cathode structure is formed.

The hole transport layer is known to be composed of polyphenylhydrocarbon or an anthracene derivative (see, for example, U.S. Pat.Nos. 6,596,415 and 6,465,115).

Organic EL devices including hole transport layers composed ofconventional materials are not satisfactory in terms of lifespan,efficiency and power consumption, and thus a material for a holetransport layer with a significant improvement in such characteristicsis required.

SUMMARY OF THE INVENTION

The present invention provides an organic layer material which haselectric stability, superior charge transport ability, and high glasstransition temperature, can prevent crystallization, and is suitable forfluorescent and phosphorescent devices having all colors, including red,green, blue, and white colors, etc., and a method of preparing the same.

The present invention also provides an organic EL device using anorganic layer composed of the above-described material and having highefficiency, low voltage, high luminance and long lifespan.

According to an aspect of the present invention, there is provided aphenylcarbazole-based compound represented by Formula (1):

where X is a substituted or unsubstituted C1-C30 alkylene group, asubstituted or unsubstituted C2-C30 alkenylene group, a substituted orunsubstituted C6-C30 arylene group, a substituted or unsubstitutedC2-C30 heteroarylene group, or a substituted or unsubstituted C2-C30heterocyclic group; each of R₁, R₂, R₃, R₁′, R₂′ and R₃′ isindependently a hydrogen atom, a substituted or unsubstituted C1-C30alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, asubstituted or unsubstituted C6-C30 aryl group, a substituted orunsubstituted C6-C30 aryloxy group, a substituted or unsubstitutedC2-C30 heterocyclic group, a substituted or unsubstituted C6-C30condensed polycyclic group, a hydroxy group, a cyano group, or asubstituted or unsubstituted amino group, and, alternatively, two ormore adjacent groups among R₁, R₂, R₃, R₁′, R₂′ and R₃′ can be connectedto each other to form a saturated or unsaturated carbocycle; and each Aris independently a substituted or unsubstituted C6-C30 aryl group or asubstituted or unsubstituted C2-C30 heteroaryl group.

According to another aspect of the present invention, there is providedan organic EL device including a first electrode, a second electrode,and an organic layer interposed therebetween, in which the organic layercontains the phenylcarbazole-based compound.

The organic layer may be a hole injection layer, a hole transport layer,or a single layer serving as both the hole injection layer and the holetransport layer.

In an embodiment of the present invention, the organic layer is a holeinjection layer or a hole transport layer, and the organic EL device hasa first electrode/hole injection layer/emitting layer/second electrodestructure, a first electrode/hole injection layer/emitting layer/holetransport layer/second electrode structure, or a firstelectrode/emitting layer/hole transport layer/second electrodestructure.

The organic layer is an emitting layer, in which the emitting layer iscomposed of a phosphorescent or fluorescent material.

In the emitting layer, the phenylcarbazole-based compound represented byFormula (1) is used as a fluorescent or phosphorescent host.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention, and many of theabove and other features and advantages of the present invention, willbe readily apparent as the same becomes better understood by referenceto the following detailed description when considered in conjunctionwith the accompanying drawings in which like reference symbols indicatethe same or similar components, wherein:

FIG. 1 is a cross-sectional view of an organic electroluminescent deviceaccording to an embodiment of the present invention;

FIG. 2 illustrates a UV spectrum of Compound represented by Formula 3obtained according to an embodiment of the present invention;

FIGS. 3 and 4 illustrate differential scanning calorimetry (DSC) andthermo gravimetric analysis (TGA) results of Compound represented byFormula 3 obtained according to an embodiment of the present invention;

FIG. 5 illustrates a UV spectrum of Compound represented by Formula 4obtained according to another embodiment of the present invention;

FIGS. 6 and 7 illustrate DSC and TGA analysis results of Compoundrepresented by Formula 4 obtained according to an embodiment of thepresent invention;

FIG. 8 is a graph illustrating the variation in luminance with respectto the current density in organic EL devices obtained in Example 1 ofthe present invention and Comparative Example 1;

FIG. 9 is a graph illustrating the variation in current efficiency withrespect to the luminance in organic EL devices obtained in Example 1 ofthe present invention and Comparative Example 1;

FIG. 10 is a graph illustrating the driving voltage at the same currentdensity for the organic EL devices according to the Example 2 andComparative Example 2;

FIG. 11 is a graph illustrating the current efficiency at the samecurrent density for the organic EL devices according to the Example 2and Comparative Example 2;

FIG. 12 shows luminance according to driving voltages in the organic ELdevices of Examples 3-6 according to the embodiments of the presentinvention and Comparative Examples 3 and 4;

FIG. 13 shows lifetime characteristics of the organic EL devices ofExamples 3, 4, 5 and 6 according to embodiments of the present inventionand the organic EL devices of Comparative Examples 3 through 6;

FIG. 14 shows a cyclic voltammogram of Compound 3 according to anembodiment of the present invention;

FIG. 15 shows a cyclic voltammogram of TLB1;

FIG. 16 shows a cyclic voltammogram of Compound 5 according to anembodiment of the present invention; and

FIG. 17 shows a cyclic voltammogram of Compound 28.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described in more detail.

The present invention provides a phenylcarbazole-based compound havingat least two phenylcarbazole derivatives as side chains in a molecule, amethod of preparing the same, and an organic EL device using thecompound as a material for an organic layer such as a hole injectionlayer, a hole transport layer, or an emitting layer.

The phenylcarbazole-based compound may be preferably represented byFormula 1:

where X is a substituted or unsubstituted C1-C30 alkylene group, asubstituted or unsubstituted C2-C30 alkenylene group, a substituted orunsubstituted C6-C30 arylene group, a substituted or unsubstitutedC2-C30 heteroarylene group, or a substituted or unsubstituted C2-C30heterocyclic group; each of R₁, R₂, R₃, R₁′, R₂′ and R₃′ isindependently a hydrogen atom, a substituted or unsubstituted C1-C30alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, asubstituted or unsubstituted C6-C30 aryl group, a substituted orunsubstituted C6-C30 aryloxy group, a substituted or unsubstitutedC2-C30 heterocyclic group, a substituted or unsubstituted C6-C30condensed polycyclic group, a hydroxy group, a cyano group, or asubstituted or unsubstituted amino group, and, alternatively, two ormore adjacent groups among R₁, R₂, R₃, R₁′, R₂′ and R₃′ can be connectedto each other to form a saturated or unsaturated carbocycle; and each Aris independently a substituted or unsubstituted C6-C30 aryl group or asubstituted or unsubstituted C2-C30 heteroaryl group.

For example, each Ar may be a phenyl group, an ethylphenyl group, anethylbiphenyl group, an o-, m-, or p-fluorophenyl group, adichlorophenyl group, a dicyanophenyl group, a trifluoromethoxyphenylgroup, an o-, m-, or p-tolyl group, an o-, m-, and p-cumenyl group, amesityl group, a phenoxyphenyl group, a (α,α-dimethylbenzene)phenylgroup, a (N,N′-dimethyl)aminophenyl group, a (N,N′-diphenyl)aminophenylgroup, a pentalenyl group, an indenyl group, a naphthyl group, amethylnaphthyl group, an anthracenyl group, an azulenyl group, aheptalenyl group, an acenaphthylenyl group, a phenanthrenyl group, afluorenyl group, an anthraquinolyl group, a triphenylene group, apyrenyl group, a perylenyl group, a chloroperylenyl group, a pentaphenylgroup, a pentacenyl group, a tetraphenylenyl group, a hexaphenyl group,a coronenyl group, a trinaphthylenyl group, a heptaphenyl group, or acarbazolyl group.

Preferably, Ar may be a phenyl group, a lower alkylphenyl group, a loweralkoxyphenyl group, a cyanophenyl group, a phenoxyphenyl group, ahalophenyl group, a naphthyl group, a lower alkylnaphthyl group, a loweralkoxynaphthyl group, a cyanonaphthyl group, a halonaphthyl group, afluorenyl group, a carbazolyl group, a lower alkylcarbazolyl group, abiphenyl group, a lower alkylbiphenyl group, a lower alkoxybiphenylgroup, a thiophenyl group, an indolyl group, or a pyridyl group. Thelower alkyl and lower alkoxy may have 1-5 carbon atoms. More preferably,Ar is a monocyclic, bicyclic, or tricyclic aryl group selected from afluorenyl group, a carbazolyl group, a phenyl group, a naphthyl group,and a phenanthrenyl group, or an aryl group substituted with one tothree, preferably, one C1-C3 lower alkyl, C1-C3 lower alkoxy, cyano,phenoxy, phenyl, or halogen on an aromatic ring thereof.

In Formula (1), one or more atoms of Ar may be substituted with a C1-C10alkyl group, a C1-C10 alkoxy group, a nitro group, a halogen atom, anamino group, a C6-C10 aryl group, a C2-C10 heteroaryl group, a cyanogroup, a hydroxy group, etc.

The phenylcarbazole-based compound represented by Formula (1) has a highglass transition point or melting point due to a rigid carbazole groupin its structure. Thus, the organic layer composed of thephenylcarbazole-based compound represented by Formula (1) has anincreased resistance to joule heat generated in organic layers, betweensuch organic layers, or between such an organic layer and a metalelectrode when electroluminescence occurs, and an increased resistanceto high temperature conditions, compared with the conventional organiclayer. Therefore, when the compound represented by Formula (1) is usedas a host material of a hole injection layer, a hole transport layer, oran emitting layer, it exhibits high luminance and can emit light for along time. In particular, since this compound has at least two rigidcarbazole groups in its molecule, the effects are further increased.

The compound represented by Formula (1) may be preferably a compoundrepresented by Formula (2):

where each of R₁ to R₃ and R₁′ to R₃′ is independently a hydrogen atom,a fluorine atom, a cyano group, a substituted or unsubstituted C1-C30alkyl group, a substituted or unsubstituted C6-C30 aryl group, asubstituted or unsubstituted C2-C30 heterocyclic group, or a substitutedor unsubstituted amino group; and each of R and R′ is a hydrogen atom, acyano group, a fluorine atom, a substituted or unsubstituted C1-C30alkyl group, a substituted or unsubstituted C6-C30 aryl group, asubstituted or unsubstituted C2-C30 heterocyclic group, or a substitutedor unsubstituted amino group.

An organic EL device of the present invention has high durability whenit is stored and operated. This is because the phenylcarbazolederivative has a high glass transition temperature Tg. The compoundrepresented by Formula (1) serves as a hole injection material, a holetransport material, and/or an emitting material. Representativestructures of embodiments of the present invention are represented byFormulae 3 through 27, but are not limited thereto:

In the specification, the compounds represented by Formulae 3 through 27are also referred to as the compounds 3 through 27, respectively.

An exemplary method of preparing one exemplary phenylcarbazole-basedcompound represented by Formula (1) will now be described.

As set forth in the reaction scheme 1, the phenylcarbazole-basedcompound represented by Formula (1a) is obtained by reacting carbazole(B′) with a diamine compound (C′).

In above Reaction Scheme 1, X is a substituted or unsubstituted C1-C30alkylene group, a substituted or unsubstituted C2-C30 alkenylene group,a substituted or unsubstituted C6-C30 arylene group, a substituted orunsubstituted C2-C30 heteroarylene group, or a substituted orunsubstituted C2-C30 heterocyclic group; each of R₁, R₂ and R₃ isindependently a hydrogen atom, a substituted or unsubstituted C1-C30alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, asubstituted or unsubstituted C6-C30 aryl group, a substituted orunsubstituted C6-C30 aryloxy group, a substituted or unsubstitutedC2-C30 heterocyclic group, a substituted or unsubstituted C6-C30condensed polycyclic group, a hydroxy group, a cyano group, or asubstituted or unsubstituted amino group, and, alternatively, two ormore adjacent groups among R₁, R₂ and R₃ on each side can be connectedto each other to form a saturated or unsaturated carbocycle; each Ar isindependently a substituted or unsubstituted C6-C30 aryl group or asubstituted or unsubstituted C2-C30 heteroaryl group; and Y is a halogenatom.

The reaction is carried out in the presence of Pd₂(dba)₃(dba=dibenzylideneacetone), sodium tert-butoxide, andtri(tert-butyl)phosphine at a temperature of 50 to 150° C.

In the organic EL device of the present invention, an organic layercontaining the phenylcarbazole-based compound represented by Formula (1)may be a hole injection layer or a hole transport layer, or a singlelayer serving as both a hole injection layer and a hole transport layer.An organic layer containing the phenylcarbazole-based compoundrepresented by Formula (1) may be an emitting layer.

When the organic layer containing the phenylcarbazole-based compoundrepresented by Formula (1) is a hole injection layer or a hole transportlayer, the device has a first electrode/hole injection layer/emittinglayer/second electrode structure, a first electrode/hole injectionlayer/emitting layer/hole transport layer/second electrode structure, ora first electrode/emitting layer/hole transport layer/second electrodestructure, but not limited thereto.

The emitting layer is composed of a phosphorescent or fluorescentmaterial.

When the organic layer containing the phenylcarbazole-based compoundrepresented by Formula (1) is the emitting layer, thephenylcarbazole-based compound is used as a fluorescent orphosphorescent host.

A method of manufacturing an organic electroluminescent device accordingto an embodiment of the present invention will now be described.

FIG. 1 is a cross-sectional view of an organic electroluminescent deviceaccording to an embodiment of the present invention.

First, a material for forming an anode, which has a high work function,is deposited or sputtered on a substrate to form an anode. Any substrateused in a conventional organic EL device can be used, and a glasssubstrate or a transparent plastic substrate having good mechanicalstrength, thermal stability, transparency, surface softness,manageability, and water-proofness may be preferably used. The anode maybe composed of indium tin oxide (ITO), indium zinc oxide (IZO), tinoxide (SnO₂), or zinc oxide (ZnO), which is transparent and have goodconductivity.

Next, a hole injection layer (HIL) is formed on the anode using a vacuumevaporation, spin coating, casting, or Langmuir-Blodgett (LB) method.The HIL may be formed using the vacuum evaporation method, since it iseasy to obtain uniform film quality and the generation of pinholes issuppressed.

When the HIL is formed using the vacuum evaporation method, thedeposition conditions can be varied according to the type of compoundused as a hole injection material, and the desired structure and thermalproperty of the HIL, but may include a deposition temperature of 50 to500° C., a vacuum of 10⁻⁸ to 10⁻³ torr, a deposition rate of 0.01 to 100Å/sec, and a film thickness of 10 Å to 5 μm.

A HIL material is not particularly restricted, but may be the compoundrepresented by Formula (1), a phthalocyanine-based compound, such asCuPc, as disclosed in U.S. Pat. No. 4,356,429 which is incorporatedherein by reference, or a Starburst type amine derivatives, for example,TCTA, m-MTDATA, or m-MTDAPB, as described in Advanced Material, 6, p.677 (1994) which is incorporated herein by reference.

Then, a hole transport layer (HTL) is formed on the HIL using a vacuumevaporation, spin coating, casting, or Langmuir-Blodgett method. The HTLmay be formed using the vacuum evaporation method, since it is easy toobtain uniform film quality and the generation of pinholes issuppressed. When the HTL is formed using the vacuum evaporation method,the deposition conditions vary according to the type of compound to beused, but may be almost identical to the deposition conditions for theHIL.

A HTL material is not particularly restricted, but may be thephenylcarbazole-based compound represented by Formula (1), or anycompound known to be used in the HTL. For example, carbazolederivatives, such as N-phenylcarbazole and polyvinylcarbazole, generalamine derivatives having an aromatic condensed ring, such asN,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine(TPD), N,N′-di(naphthalen-1-yl)-N,N′-diphenyl benzidine (α-NPD), etc.are used.

Then, an emitting layer (EML) is formed on the HTL using a vacuumevaporation, spin coating, casting, or Langmuir-Blodgett method. The EMLmay be formed using the vacuum evaporation method since it is easy toobtain uniform film quality and the generation of pinholes issuppressed. When the EML is formed using the vacuum evaporation method,the deposition conditions vary according to the type of compound to beused, but may be almost identical to the deposition conditions for theHIL.

An EML material is not particularly restricted, but may be thephenylcarbazole-based compound represented by Formula (1) as afluorescent or phosphorescent host. Alq₃ (tris(8-quinolinolate)aluminum) may be used as a fluorescent host. IDE102 and IDE105 availablefrom Idemitsu Kosan Co., Ltd., and C545T available from Hayashibara maybe used as fluorescent dopants, and Ir(PPy)₃ (PPy=phenylpyridine)(green), F2Irpic (bis[2-(4,6-difluorophenyl)pyridinato-N,C2′]iridiumpicolinate) (blue), and RD61 (red) may be vacuum evaporated (doped) incombination as phosphorescent dopants.

The concentration of the dopant is not particularly restricted, but istypically 0.01-15 parts by weight based of total 100 parts by weight ofthe host and the dopant.

When the phosphorescent dopant is used in the EML, a hole blockingmaterial is vacuum evaporated or spin coated on the EML to form a holeblocking layer (HBL), in order to prevent a triplet exciton or a holefrom diffusing into the ETL. The hole blocking material is notparticularly restricted, but may be selected from materials which areused as a hole blocking material in the art. For example, oxadiazolederivatives or triazole derivatives, phenanthroline derivatives, or holeblocking materials described in JP 11-329734 (A1) which is incorporatedherein by reference and the like may be used and, more particularly,bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (BAlq),2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) are used.

Then, an electron transport layer (ETL) is formed using a vacuumevaporating, spin coating, or casting method. Preferably, the ETL isformed using the vacuum evaporating method. An ETL material may be anymaterial which can stably transport electrons injected from an electroninjection electrode (cathode) and, more particularly,tris(8-quinolinolate) aluminum (Alq₃) may be used. In addition, anelectron injection layer (EIL) for facilitating the injection ofelectrons from the cathode may be deposited on the ETL and a materialfor the injection layer is not particularly restricted.

LiF, NaCl, CsF, Li₂O, BaO, etc. may be used as the EIL material. Thedeposition conditions of the HBL, the ETL, and the EIL vary according tothe type of compound to be used, but may be almost identical to thedeposition conditions for HIL.

Finally, a metal for a cathode is vacuum evaporated or sputtered on theEIL to form a cathode. The metal for a cathode may be a metal having alow work function, alloy, electric conducting compound, and a mixturethereof. Examples of such a material include Li, Mg, Al, Al—Li, Ca,Mg—In, or Mg—Ag. Also, a transmittance type cathode composed of ITO orIZO may form a front surface of the light emitting device.

The organic EL device according to an embodiment of the presentinvention may include one or two intermediate layers in addition to theanode, the HIL, the HTL, the EML, the ETL, the EIL, and the cathode asillustrated in FIG. 1.

The compound represented by Formula (1) is useful as a light emittingmaterial having superior light emitting property and hole transportproperty, in particular, as a host, and may also be used as a holeinjection material and/or a hole transport material of blue, green, redfluorescent and phosphorescent devices.

Representative groups used in Formula (1) will now be defined.

Specific examples of the unsubstituted C1-C30 alkyl group in Formula (1)include methyl, ethyl, propyl, isobutyl, sec-butyl, pentyl, iso-amyl,hexyl, and the like. The hydrogen atoms of the alkyl group may beunsubstituted, or at least one hydrogen atom on the alkyl group may besubstituted with a halogen atom, a C1-C30 alkyl group, a C1-C30 alkoxygroup, a lower alkylamino group, a hydroxy group, a nitro group, a cyanogroup, an amino group, an amidino group, hydrazine, hydrazone, acarboxyl group, a sulfonic acid group, a phosphoric acid group, etc.

Specific examples of the unsubstituted C2-C30 alkenyl group in Formula(1) include an ethylene group, a propylene group, an isobutylene group,a vinyl group, and an allyl group. The hydrogen atoms of the alkenylgroup may be unsubstituted, or at least one hydrogen atom on the alkenylgroup may be substituted with a halogen atom, a C1-C30 alkyl group, aC1-C30 alkoxy group, a lower alkylamino group, a hydroxy group, a nitrogroup, a cyano group, an amino group, an amidino group, hydrazine,hydrazone, a carboxyl group, a sulfonic acid group, a phosphoric acidgroup, etc.

Specific examples of the unsubstituted C1-C30 alkoxy group in Formula(1) include methoxy, ethoxy, propoxy, isobutyloxy, sec-butyloxy,pentyloxy, iso-amyloxy, and hexyloxy. The hydrogen atoms of the alkoxygroup may be unsubstituted, or at least one hydrogen atom on the alkoxygroup may be substituted with the same substituent as in theabove-described C1-C20 alkyl group.

The aryl group in Formula (1) is a carbocyclic aromatic system thatincludes one or more rings, in which the rings may be attached or fusedby a pendent method. Specific examples of the aryl group include phenyl,naphthyl, tetrahydronaphthyl, and the like. The hydrogen atoms of thearyl group may be unsubstituted, or at least one hydrogen atom on thearyl group may be substituted with the same substituent as in theabove-described C1-C20 alkyl group.

The heteroaryl group in Formula (1) is a monovalent monocyclic ringsystem, which contains one, two or three heteroatoms selected from N, O,P, and S and has carbon atoms as the remaining ring atoms, in which therings may be attached or fused by a pendent method. Examples of such aheteroaryl group include pyridyl, thienyl, furyl, and the like.

The heterocyclic group in Formula (1) is a monocyclic system, whichcontains one, two or three heteroatoms selected from N, O, P, and S andhas carbon atoms as the remaining ring atoms, in which some hydrogenatoms on the cycloalkyl group are substituted with lower alkyl groups.At least one hydrogen atom on the cycloalkyl group may be substitutedwith the same substituent as in the above-described C1-C20 alkyl group.

The present invention will be described in greater detail with referenceto the following examples. The following examples are for illustrativepurposes and are not intended to limit the scope of the invention.

SYNTHESIS EXAMPLE 1 Preparation of Compound Represented by Formula 3

Compound represented by Formula 3 (i.e., Compound 3) was synthesizedaccording to the reaction scheme 2.

Synthesis of Intermediate Compound A

Carbazole (16.7 g, 100 mmol), iodobenzene (26.5 g, 130 mmol), CuI (1.9g, 10 mmol), K₂CO₃ (138 g, 1 mol), and 18-crown-6 (530 mg, 2 mmol) weredissolved in 1,3-dimethyl-3,4,5,6-tetrahydro-(1H)-pyrimidinone (DMPU)(500 mL), and then heated at 170° C. for 8 hrs.

After the reaction was completed, the reaction mixture was cooled toroom temperature and solid materials were filtered. A small amount ofaqueous ammonia was added to the filtrate, and the resultant was threetimes washed with diethyl ether (300 mL). The washed diethyl ether layerwas dried on MgSO₄ and dried under reduced pressure to obtain a crudeproduct. The crude product was purified with a silica gel columnchromatography to obtain 22 g of the intermediate compound A as a whitesolid (yield: 90%).

¹H NMR (CDCl₃, 400 MHz) δ (ppm) 8.12 (d, 2H), 7.58-7.53 (m, 4H),7.46-7.42 (m, 1H), 7.38 (d, 4H), 7.30-7.26 (m, 2H); ¹³C NMR (CDCl₃, 100MHz) δ (ppm) 141.0, 137.9, 130.0, 127.5, 127.3, 126.0, 123.5, 120.4,120.0, 109.9.

Synthesis of Intermediate Compound B

2.433 g (10 mmol) of the intermediate compound A was added to 100 mL of80% acetic acid, and then 1.357 g (5.35 mmol) of iodine (I₂) and 0.333 g(1.46 mmol) of ortho-periodinic acid (H₅IO₆) were added thereto. Theresultant was stirred under nitrogen atmosphere at 80° C. for 2 hrs.

After the reaction was completed, the reaction mixture was three timesextracted with ethyl ether (50 mL). The collected organic layer wasdried on magnesium sulfate and the solvent was evaporated. The residuewas purified with a silica gel column chromatography to obtain 3.23 g ofthe intermediate compound B as a white solid (yield: 87%).

¹H NMR (CDCl₃, 300 MHz) δ (ppm) 8.43 (d, 1H), 8.05 (d, 1H), 7.62 (dd,1H), 7.61-7.75 (m, 2H), 7.51-7.43 (m, 3H), 7.41-7.35 (m, 2H), 7.27 (dd,1H), 7.14 (d, 1H)

Synthesis of Intermediate Compound C

3.12 g (10 mmol) of 4,4′-dibromodiphenyl, 2.3 mL (25 mmol) of aniline,2.9 g (30 mmol) of t-BuONa, 183 mg (0.2 mmol) of Pd₂(dba)₃, and 20 mg(0.1 mmol) of P(t-Bu)₃ were dissolved in 30 mL of toluene, and thenstirred at 90° C. for 3 hrs.

The reaction mixture was cooled to room temperature and three timesextracted with distilled water and diethyl ether. Precipitates in anorganic layer were filtered, washed with acetone and diethyl ether, andthen dried in vacuum to obtain 0.3 g of the intermediate compound C(yield: 90%). The structure of the intermediate compound C wasidentified with ¹H NMR.

¹H NMR (DMSO-d₆, 400 MHz) δ (ppm) 8.22 (s, 2H), 7.48 (d, 4H), 7.23 (t,4H), 7.10 (dd, 8H), 6.82 (t, 2H); ¹³C NMR (DMSO-d₆, 100 MHz) δ (ppm)145.7, 144.3, 133.7, 131.4, 128.7, 121.2, 119.2, 118.9.

Synthesis of Compound Represented by Formula 3

912 mg (2.47 mmol) of the intermediate compound B, 336.4 mg (1 mmol) ofthe intermediate compound C, 300 mg (3 mmol) of t-BuONa, 40 mg (0.02mmol) of Pd₂(dba)₃, and 3 mg (0.01 mmol) of P(t-Bu)₃ were dissolved in 5mL of toluene, and then stirred at 90° C. for 3 hrs.

After the reaction was completed, the resultant was cooled to roomtemperature and three times extracted with distilled water and diethylether. The collected organic layer was dried on magnesium sulfate andthe solvent was evaporated. The residue was purified with a silica gelcolumn chromatography to obtain 570 mg of Compound represented byFormula 3 as a yellow solid (yield: 70%).

¹H NMR (CDCl₃, 300 MHz) δ (ppm) 7.99 (d, 2H), 7.95 (s, 2H), 7.61-7.57(m, 8H), 7.48-7.32 (m, 12H), 7.27-7.19 (m, 8H), 7.18-7.10 (m, 8H), 6.96(t, 2H); ¹³C NMR (CDCl₃, 100 MHz) δ (ppm) 148.4, 147.3, 141.3, 140.4,138.0, 137.6, 133.9, 129.9, 129.1, 127.4, 127.1, 127.0, 126.1, 125.6,124.3, 123.0, 122.9, 122.8, 121.7, 120.5, 119.9, 118.5, 110.7, 109.9.

The obtained Compound represented by Formula 3 was diluted with CHCl₃ toa concentration of 0.2 mM and the UV spectrum therefor was obtained. Amaximum absorption wavelength of 351 nm was observed in the UV spectrum(FIG. 2).

Further, Compound represented by Formula 3 was subjected to thermalanalysis using TGA (Thermo Gravimetric Analysis) and DSC (DifferentialScanning Calorimetry) (N₂ atmosphere, temperature range: roomtemperature—600° C. (10° C./min)—TGA, room temperature—400° C.—DSC, Pantype: Pt pan in disposable Al pan (TGA), disposable Al pan (DSC)) toobtain Td 494° C. and Tg 153° C. (FIGS. 3 and 4).

A HOMO (Highest Occupied Molecular Orbital) energy level of 5.16 eV anda LUMO (Lowest Occupied Molecular Orbital) energy level of 2.16 eV wereobtained using UV absorption spectrum and a potentiometer AC-2.

SYNTHESIS EXAMPLE 2 Preparation of Compound Represented by Formula 4

Compound represented by Formula 4 (i.e., Compound 4) was synthesizedaccording to the reaction scheme 3.

Synthesis of Intermediate Compound D

3.69 g (10 mmol) of the intermediate compound B, 1.42 g (12 mmol) of4-aminobenzonitrile, 1.44 g (15 mmol) of t-BuONa, 183 mg (0.2 mmol) ofPd₂(dba)₃, and 40 mg (0.2 mmol) of P(t-Bu)₃ were dissolved in 50 mL oftoluene, and then stirred at 90° C. for 3 hrs.

After the reaction was completed, the reaction mixture was cooled toroom temperature and three times extracted with distilled water anddiethyl ether. The collected organic layer was dried on magnesiumsulfate and the solvent was evaporated. The residue was purified with asilica gel column chromatography to obtain 1.8 g of the intermediatecompound D (yield: 50%).

Synthesis of Compound represented by Formula 4

222 mg (0.61 mmol) of the intermediate compound D, 78 mg (0.25 mmol) of4,4′-dibromodiphenyl, 80 mg (0.75 mmol) of t-BuONa, 310 mg (0.01 mmol)of Pd₂(dba)₃, and 2 mg (0.01 mmol) of P(t-Bu)₃ were dissolved in 5 mL oftoluene, and then stirred at 90° C. for 3 hrs.

After the reaction was completed, the reaction mixture was cooled toroom temperature and three times extracted with distilled water anddiethyl ether. The collected organic layer was dried on magnesiumsulfate and the solvent was evaporated. The residue was purified with asilica gel column chromatography to obtain 186 mg of Compoundrepresented by Formula 4 as a yellow solid (yield: 86%).

¹H NMR (CDCl₃, 300 MHz) δ (ppm) 8.02 (d, 2H), 7.97 (d, 2H), 7.64-7.48(m, 14H), 7.43-7.39 (m, 10H), 7.29-7.22 (m, 8H), 7.03 (d, 4H); ¹³C NMR(CDCl₃, 100 MHz) δ (ppm) 152.1, 145.6, 141.5, 138.9, 138.2, 137.3,136.3, 133.2, 130.0, 127.9, 127.8, 127.0, 126.6, 125.8, 125.5, 124.6,122.7, 120.5, 120.2, 119.9, 119.4, 118.9, 111.2, 110.1, 101.8.

The obtained Compound represented by Formula 4 was diluted with CHCl₃ toa concentration of 0.2 mM and the UV spectrum therefor was obtained. Amaximum absorption wavelength of 351 nm was observed in the UV spectrum(FIG. 5).

Further, Compound represented by Formula 4 was subjected to thermalanalysis using TGA and DSC (N₂ atmosphere, temperature range: roomtemperature—600° C. (10° C./min)—TGA, room temperature—400° C.—DSC, Pantype: Pt pan in disposable Al pan (TGA), disposable Al pan (DSC)) toobtain Td 490° C., Tg 178° C., and Tm of 263° C. (FIGS. 6 and 7).

A HOMO energy level of 5.30 eV and a LUMO energy level of 2.37 eV wereobtained using UV absorption spectrum and a potentiometer AC-2.

SYNTHESIS EXAMPLE 3 Preparation of Compound Represented by Formula 5

Compound represented by Formula 5 (i.e., Compound 5) was synthesizedthrough Reaction Scheme 3 below.

Intermediate E was synthesized by reacting 4,4′-dibromodiphenyl andp-tolylamine in the same manner as in the synthesis of Intermediate C(yield: 85%). 678 mg of Compound 5 as a yellow solid was obtained byreacting Intermediates B and E in the same manner as in the synthesis ofCompound 3 (yield: 80%).

¹H NMR (C₆D₆, 400 MHz) δ (ppm) 8.14 (d, 2H), 7.64 (d, 2H), 7.47 (d, 4H),7.38-7.28 (m, 6H), 7.27-7.25 (m, 8H), 7.23-7.01 (m, 16H), 6.96 (d, 2H),2.19 (s, 6H); ¹³C NMR (C₆D₆, 100 MHz) δ (ppm) 149.0, 147.5, 142.6,142.2, 139.1, 138.9, 135.1, 132.6, 130.1, 130.7, 128.1, 127.9, 127.2,126.5, 125.9, 125.0, 124.5, 123.6, 121.8, 121.1, 119.2, 111.8, 110.8,21.5.

The obtained Compound 5 was diluted with CHCl₃ to a concentration of 0.2mM and the UV spectrum therefor was obtained. Maximum absorptionwavelengths of 358, 309, and 253 nm were observed in the UV spectrum.

Further, Compound 5 was subjected to thermal analysis using ThermoGravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC)(N₂ atmosphere, temperature range: room temperature—600° C. (10°C./min)—TGA, room temperature—400° C.—DSC, Pan Type Pt Pan in disposalAl Pan (TGA), disposable Al pan (DSC)) to obtain Td 480° C. and Tg 155°C.

A Highest Occupied Molecular Orbital (HOMO) energy level of 5.0 eV and aLowest Occupied Molecular Orbital (LUMO) energy level of 2.02 eV wereobtained using a UV absorption spectrum and a potentiometer AC-2.

SYNTHESIS EXAMPLE 4 Preparation of Compound Represented by Formula 7

Compound represented by Formula 7 (i.e., Compound 7) was synthesizedthrough Reaction Scheme 5 below.

Intermediate F was synthesized by reacting 4,4′-dibromodiphenyl and4-aminobiphenyl in the same manner as in the synthesis of Intermediate C(yield: 98%). 826 mg of Compound 7 as a yellow solid was obtained byreacting Intermediates B and F in the same manner as in the synthesis ofCompound 3 (yield: 85%).

¹H NMR (CD₂Cl₂, 400 MHz) δ (ppm) 8.02-8.01 (m, 4H), 7.65-7.56 (m, 12H),7.51-7.46 (m, 10H), 7.43-7.36 (m, 10H), 7.32-7.17 (m, 14H); ¹³C NMR(CD₂Cl₂, 100 MHz) δ (ppm) 148.2, 147.6, 141.8, 141.0, 140.6, 138.6,137.9, 134.5, 134.4, 130.3, 129.1, 127.9, 127.8, 127.4, 127.3, 127.0,126.8, 126.6, 126.1, 124.7, 123.5, 123.4, 123.0, 120.8, 120.3, 119.0,111.1, 110.3.

The obtained Compound 7 was diluted with CHCl₃ to a concentration of 0.2mM and the UV spectrum therefor was obtained. A maximum absorptionwavelength of 329 nm was observed in the UV spectrum.

Further, Compound 7 was subjected to thermal analysis using TGA and DSC(N₂ atmosphere, temperature range: room temperature—600° C. (10°C./min)—TGA, room temperature—400° C.—DSC, Pan Type: Pt Pan in disposalAl Pan (TGA), disposal Al pan (DSC)) to obtain Td 533° C. and Tg 174° C.

A HOMO energy level of 5.2 eV and a LUMO energy level of 2.27 eV wereobtained using a UV absorption spectrum and a potentiometer AC-2.

SYNTHESIS EXAMPLE 5 Preparation of Compound Represented by Formula 27

Compound represented by Formula 27 (i.e., Compound 27) was synthesizedthrough Reaction Scheme 6 below.

Intermediate G was synthesized by reacting 4,4′-dibromodiphenyl and4-fluorophenylamine in the same manner as in the synthesis ofIntermediate C (yield: 95%). 718 mg of Compound 27 as a yellow solid wasobtained by reacting Intermediates B and G in the same manner as in thesynthesis of Compound 3 (yield: 84%).

¹H NMR (C₆D₆, 400 MHz) δ (ppm) 8.05 (s, 2H), 7.68 (d, 2H), 7.48 (d, 4H),7.29-7.11 (m, 22H), 7.09-7.01 (m, 6H), 6.78 (t, 4H)

The obtained Compound 27 was diluted with CHCl₃ to a concentration of0.2 mM and the UV spectrum therefor was obtained. Maximum absorptionwavelengths of 351, 297, and 248 nm were observed in the UV spectrum.

Further, Compound 27 was subjected to TGA and DSC (N₂ atmosphere,temperature range: room temperature—600° C. (10° C./min)—TGA, roomtemperature—400° C.—DSC, Pan Type Pt Pan in disposal Al Pan (TGA),disposal Al pan (DSC)) to obtain Td 464° C., Tg 151° C., and Tm 299° C.

A HOMO energy level of 5.1 eV and a LUMO energy level of 2.28 eV wereobtained using a UV absorption spectrum and a potentiometer AC-2.

SYNTHESIS REFERENCE EXAMPLE 1 Preparation of Compound Represented byFormula 28

Compound represented by Formula 28 (i.e., Compound 28) was synthesizedthrough Reaction Scheme 7 below.

Intermediate B-1 was synthesized in the same manner as in the synthesisof Intermediate B (yield: 92%). 586 mg of Compound 28 as a yellow solidwas obtained by reacting Intermediates B-1 and E in the same manner asin the synthesis of Compound 3 (yield: 78%).

¹H NMR (CD₂Cl₂, 400 MHz) δ (ppm) 7.96-7.91 (m, 4H), 7.43-7.06 (m, 26H),4.37 (q, 4H), 2.31 (s, 6H), 1.43 (t, 6H); ¹³C NMR (CD₂Cl₂, 100 MHz) δ(ppm) 148.1, 146.3, 140.8, 139.9, 137.5, 133.4, 132.1, 130.0, 127.1,126.1, 125.7, 124.1, 123.9, 122.9, 122.0, 120.7, 119.0, 118.9, 109.7,109.0, 38.0, 20.8, 14.0.

SYNTHESIS REFERENCE EXAMPLE 2 Preparation of Compound Represented byFormula 29

Compound represented by Formula 29 (i.e., Compound 29) was synthesizedthrough Reaction Scheme 8 below.

Intermediate B-1 was synthesized in the same manner as in the synthesisof Intermediate B (yield: 92%). 630 mg of Compound 29 as a yellow solidwas obtained by reacting Intermediates B-1 and G in the same manner asin the synthesis of Compound 3 (yield: 83%).

¹H NMR (CD₂Cl₂, 400 MHz) δ (ppm) 7.96 (d, 2H), 7.88 (d, 2H), 7.46-6.92(m, 26H), 4.35 (q, 4H), 1.44 (t, 3H); ¹³C NMR (CD₂Cl₂, 100 MHz) δ (ppm)158.2 (d), 147.6, 144.6, 140.0, 139.3, 137.1, 133.4, 127.0, 125.8,125.2, 125.1, 125.0, 123.2 (d), 121.6, 120.6, 118.8, 118.5, 115.8 (d),109.3, 108.5, 37.6, 13.9.

Example 1

A coming 15 Ω/cm² (1200 Å) ITO glass substrate as an anode was cut to asize of 50 mm×50 mm×0.7 mm and ultrasonically washed with isopropylalcohol and pure water, for 5 min each wash. Then, the washed glasssubstrate was irradiated with a UV radiation for 30 min and washed byexposing to ozone, and then, installed in a vacuum evaporator.

Compound represented by Formula 3 was vacuum evaporated on the substrateto form a 600 Å thick HIL. Then,4,4-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was vacuumevaporated on the HIL to form a 300 Å thick HTL.

IDE140 (available from Idemitsu Kosan Co., Ltd.), which was known as ablue fluorescent host, and IDE105 (available from Idemitsu Kosan Co.,Ltd.), which was known as a blue fluorescent dopant, were co-deposited(weight ratio 98:2) on the HTL to form a 200 Å thick EML.

Alq₃ was deposited on the EML to form a 300 Å thick ETL, and then LiFwas deposited on the ETL to form a 10 Å thick EIL and Al was depositedthereon to form a 3000 Å thick anode, thereby completing an organicelectroluminescent device.

This device has a driving voltage of 7.1 V, a luminance of 3,214 cd/m²,a color coordination (0.14, 0.15), and luminous efficiency of 6.43 cd/Aat a current density of 50 mA/cm².

COMPARATIVE EXAMPLE 1

An organic EL device was manufactured in the same manner as in Example1, except that IDE 406 (available from Idemitsu Kosan Co., Ltd.) insteadof Compound represented by Formula 3 was used to form a HIL.

This device has a driving voltage of 8.0 V, a luminance of 3,024 cd/m²,a color coordination (0.14, 0.15), and luminous efficiency of 6.05 cd/Aat a current density of 50 mA/cm².

The driving voltage of the organic EL device which used Compoundrepresented by Formula 3 according to an embodiment of the presentinvention as a HIL material was approximately 1 V lower than the drivingvoltage of the organic EL device of Comparative Example 1 at the samecurrent density due to an improved charge injection ability. Further,the organic EL device of Example 1 had higher current efficiency andluminance than the organic EL device of Comparative Example 1.

The luminance and current efficiency at the same current density for theorganic EL devices are illustrated in FIGS. 8 and 9.

Example 2

A corning 15 Ω/cm² (1200 Å) ITO glass substrate as an anode was cut to asize of 50 mm×50 mm×0.7 mm and ultrasonically washed with isopropylalcohol and pure water, for 5 min each wash. Then, the washed glasssubstrate was irradiated with a UV radiation for 30 min and washed byexposing to ozone, and then, installed in a vacuum evaporator.

Compound represented by Formula 3 was vacuum evaporated on the substrateto form a 600 Å thick HIL. Then,4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was vacuumevaporated on the HIL to form a 300 Å thick HTL. Alq3, which was a greenfluorescent host and C545T, which was a green fluorescent dopant, wereco-deposited (weight ratio 98:2) on the HTL to form a 250 Å thick EML.

Alq₃ was deposited on the EML to form a 300 Å thick ETL, and then LiFwas deposited on the ETL to form a 10 Å thick EIL and Al was depositedthereon to form a 3000 Å thick anode, thereby completing an organic ELdevice.

This device has a driving voltage of 6.12 V, a luminance of 8,834 cd/m²,a color coordination (0.31, 0.63), and luminous efficiency of 17.67 cd/Aat a current density of 50 mA/cm².

COMPARATIVE EXAMPLE 2

An organic EL device was prepared in the same manner as in Example 2,except for using IDE406 (available from Idemitsu Kosan Co., Ltd.)instead of Compound represented by Formula 3 in forming a hole injectionlayer.

This device has a driving voltage of 6.73 V, a luminance of 7,083 cd/m²,a color coordination (0.31, 0.63), and luminous efficiency of 14.17 cd/Aat a current density of 50 mA/cm².

The driving voltage and current efficiency at the same current densityfor the organic EL devices according to the Example 2 and ComparativeExample 2 are illustrated in FIGS. 10 and 11.

Example 3

An organic EL device was manufactured in the same manner as in Example1, except that IDE215 (available from Idemitsu Kosan Co., Ltd.) andIDE118 (available from Idemitsu Kosan Co., Ltd.), which are known asblue fluorescent dopants instead of IDE 140 (available from IdemitsuKosan Co., Ltd.) and IDE105 (available from Idemitsu Kosan Co., Ltd.),which are the blue fluorescent dopants used in Example 1, wereco-deposited on a hole transport layer (weight ratio 98:2) to form anemitting layer (EML) having a thickness of 300 Å.

The device had a driving voltage of 7.18 V, a luminance of 7,253 cd/m²,a color coordination (0.144, 0.244), and luminous efficiency of 7.25cd/A at a current density of 100 mA/cm².

Example 4

An organic EL device was manufactured in the same manner as in Example3, except that Compound 5 instead of Compound 3 was used to form a HIL.

The device has a driving voltage of 7.07 V, a luminance of 7,715 cd/m²,a color coordination (0.144, 0.235), and luminous efficiency of 7.72cd/A at a current density of 100 mA/cm².

Example 5

An organic EL device was manufactured in the same manner as in Example3, except that Compound 7 instead of Compound 3 was used to form a HIL.

This device had a driving voltage of 6.72 V, a luminance of 7,104 cd/m²,a color coordination (0.143, 0.232), and luminous efficiency of 7.10cd/A at a current density of 100 mA/cm².

Example 6

An organic EL device was manufactured in the same manner as in Example3, except that Compound 27 instead of Compound 3 was used to form a HIL

This device had a driving voltage of 6.87 V, a luminance of 7,931 cd/m²,a color coordination (0.145, 0.246), and luminous efficiency of 7.93cd/A at a current density of 100 mA/cm².

COMPARATIVE EXAMPLE 3

An organic El device was manufactured in the same manner as Example 3,except that IDE406 (available from Idemitsu) instead of Compound 3 wasused to form a HIL.

This device had a driving voltage of 8.38 V, a luminance of 6,528 cd/m²,a color coordination (0.143, 0.243), and luminous efficiency of 6.53cd/A at a current density of 100 mA/cm².

COMPARATIVE EXAMPLE 4

An organic EL device was manufactured in the same manner as Example 3,except that N,N′-bis(9-ethylcarbazol-3-yl)-N,N′-diphenylbenzidine (TLB1)disclosed in International Publication No. WO03/008515 instead ofCompound 3 was used to form a HIL.

This device had a driving voltage of 7.25 V, a luminance of 7,104 cd/m²,a color coordination (0.143, 0.235), and luminous efficiency of 7.10cd/A at a current density of 100 mA/cm².

COMPARATIVE EXAMPLE 5

An organic EL device was manufactured in the same manner as in Example3, except that Compound 28 of Synthesis Reference Example 1, which is aderivative of TLB1, instead of Compound 3 was used to form a HIL.

This device had a driving voltage of 7.25 V, a luminance of 7,342 cd/m²,a color coordination (0.145, 0.239), and luminous efficiency of 7.34cd/A at a current density of 100 mA/cm².

COMPARATIVE EXAMPLE 6

An organic EL device was manufactured in the same manner as in Example3, except that Compound 29 of Synthesis Reference Example 2, which is aderivative of TLB1, instead of Compound 3 was used to form a HIL.

This device had a driving voltage of 7.18 V, a luminance of 7,681 cd/m²,a color coordination (0.144, 0.245), and luminous efficiency of 7.68cd/A at a current density of 100 mA/cm².

Characteristics of driving voltage, luminance, color coordination, andluminous efficiency of organic EL devices of Examples 3-6 according tothe embodiments of the present invention and Comparative Examples 3-6are shown in Table 1.

TABLE 1 Driving Color Luminous Hole injection voltage (V) Luminancecoordination efficiency material (@100 A/cm²) (cd/m²) (x, y) (cd/A)Example 3 Compound 3 7.18 7,253 (0.144, 0.244) 7.25 Example 4 Compound 57.07 7,715 (0.144, 0.235) 7.72 Example 5 Compound 7 6.72 7,104 (0.143,0.232) 7.10 Example 6 Compound 27 6.87 7,931 (0.145, 0.246) 7.93Comparative IDE 406 8.38 6,528 (0.143, 0.243) 6.53 Example 3 ComparativeTLB1 7.25 7,104 (0.143, 0.235) 7.10 Example 4 Comparative Compound 287.25 7,342 (0.145, 0.239) 7.34 Example 5 Comparative Compound 29 7.187,681 (0.144, 0.245) 7.68 Example 6

For reference, in Table 1, characteristics of driving voltage,luminance, color coordination and luminous efficiency of Compounds 3, 57 and 27 according to the embodiments of the present invention arerespectively and directly compared to those of TLB1 and Compounds 28 and29.

According to Table 1, when Compounds 3, 5, 7 and 27 were used as amaterial for a hole injection layer, charge injection capability wasimproved, and thus driving voltages were respectively reduced to 1.13 V,1.31 V, 1.66 V, and 1.51 V at the same current level, current efficiencywas improved, and luminance was improved compared to when using IDE406.

FIG. 12 shows luminance according to driving voltages in the organic ELdevices of Examples 3-6 according to the embodiments of the presentinvention and Comparative Examples 3 and 4.

Referring to FIG. 12, the organic EL devices of Examples 3-6 hadimproved luminance compared to the organic EL devices of ComparativeExample 3, and had similar luminance to that of Comparative Example 4.

FIG. 13 shows lifetime characteristics of the organic EL devices ofExamples 3, 4, 5 and 6 according to the embodiments of the presentinvention and the organic EL devices of Comparative Examples 3 through6.

Referring to FIG. 13, lifetimes of the organic EL devices of Examples3-6 and Comparative Examples 3-6 were measured at a current density of100 mA/cm² which is a condition for an accelerated lifetime test. Thelifetime was evaluated by measuring time taken for the display/pixel tofall to half its initial stated luminance. The organic EL devices ofExamples 3, 4, 5 and 6 had extended lifetime compared to those ofComparative Example 3 and 4. The lifetime characteristics of the organicEL devices of Examples 3 through 6 according to the embodiments of thepresent invention were respectively improved by 20%, 33%, 42% and 56%compared to those of the organic EL devices of Comparative Example 3which uses a known hole injection material of IDE406 (available fromIdemitsu Kosan Co., Ltd.). It is well known to those of ordinary skillin the art that the accelerated lifetime is directly in proportion tothe real lifetime of the organic EL devices.

Particularly, initial characteristics of the organic EL devices inComparative Examples 4 and 5 which use Compounds 28 and 29 were similarto initial characteristics of the organic EL devices according to theembodiments of the present invention, but lifetime thereof wasconsiderably different from lifetime of the organic EL devices accordingto the embodiments of the present invention.

Lifetimes of the organic EL devices of Examples 3-6 according to thepresent invention were longer than that of Comparative Example 4 usingTLB1 by 244%, 269%, 287%, and 315%, respectively. Also, as a result ofrespectively comparing Compound 5 with Compound 28 and Compound 27 withCompound 29 in which substituents at the N site in carbazole werevaried, the lifetimes of the organic EL devices of Compound 5 (393hours) and Compound 27 (418 hours) according to the embodiments of thepresent invention were longer than those of Compound 28 (106 hours) andCompound 29 (175 hours) by 371% and 239%, respectively.

In addition, Comparative Examples 4 through 6 clearly show a decrease inlifetime characteristics compared to a known hole injection material ofIDE406 (available from Idemitsu Kosan Co., Ltd.) in FIG. 13. When thelifetime of a device is less than 300 hours, the device is hardlycommercialized. In particular, an image sticking phenomenon may occurdue to considerable reduction in the initial luminance in ComparativeExamples 4 through 6 compared to Examples 3 through 6. “Image sticking”is a phenomenon in which the same image is continuously displayed andcauses pixels or sub-pixels to continuously output undesired signals. Inparticular, image sticking is closely associated with lifetime inself-emission systems.

These results are caused by the substituents connected to the N site ofcarbazole. TLB1 has a very unstable structure in which a radicalgenerated at the N site during transporting holes is easily disappearedsince an ethyl group which is unstable in oxidation is substituted atthe N site of carbazole. In contrast, the compounds according to thepresent invention in which a substituted or unsubstituted phenyl groupis substituted at the N site of carbazole has a fully conjugatedstructure of the entire phenylcarbazole, and thus the compounds areprotected against oxidation through external attacks and have a stablestructure of radicals generated at the N site during the transportationof holes.

These were measured using cyclic voltammetry (CV) which is anelectrochemical method for obtaining oxidation and reduction propertiesand stability of a compound. Using CV, electrochemical movement ofoxidation and reduction species can be rapidly observed in a wide rangeof electric potential. CV is a widely used electrochemical method ofdetermining the mechanism of oxidation and reduction reactions. CV ofCompound 3, TLB 1, Compounds 5 and 28 was measured using a PAR 273APotentiostat (AMETEK EG&G).

A sample having a concentration of 1×10⁻³ M was measured at a scan speedof 100 mV/sec using Ag⁺/Ag as a reference electrode, Pt (BioAnalyticalSystem, USA) as a working electrode and auxiliary electrode, anddichloromethane (HPLC grade, Mallinkrodt) solution including 0.1 Mtetrabutylammonium hexafluorophosphate (99%, Fluka) as an electrolytesolution.

As shown in FIG. 14, Compound 3 according to the embodiment of thepresent invention showed a stable state even after severaloxidation-reduction cycles. In contrast, TLB1 showed a rapid collapse ofoxidized state (FIG. 15). Further, as shown in FIG. 16, Compound 3according to the embodiment of the present invention also showed astable oxidation-reduction curve. In contrast, Compound 28 illustratedin FIG. 17 showed a very unstable state with a collapse of peaks due torepeated oxidation-reduction cycles.

One of the distinguishable properties of hole transport materials of theembodiments of the present invention is stability against externalthermal stimulus. While a glass transition temperature (Tg) of TLB1 was136° C., Tg of the phenylcarbazole-based compounds according to theembodiments of the present invention was higher than 150° C.Considerable improvement in lifetime characteristics can be obtainedbecause of differences in such structural and thermal stability.

As described above, the compounds according to the present invention areexcellent hole injection materials having low driving voltage, highefficiency, and long lifetime compared to the compounds according to thecited reference. As described above, the phenylcarbazole-based compoundsaccording to an embodiments of the present invention have superiorelectric properties and charge transport abilities, and thus are usefulas a hole injection material, a hole transport material, and/or anemitting material which is suitable for fluorescent and phosphorescentdevices of all colors, including red, green, blue, and white colors. Theorganic EL device manufactured using the phenylcarbazole-based compoundhas high efficiency, low voltage, high luminance, and a long lifespan.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A compound represented by one of formulae (5), (7) and (27):


2. A method of preparing a compound represented by Formula (1),comprising: reacting carbazole (B′ and B″) with a diamine compound (C′):

where X is a biphenyl group; each of R₁, R₂, R₃, R₁′, R₂′ and R₃′ isindependently selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted C1-C30 alkyl group, a substituted orunsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C6-C30aryl group, a substituted or unsubstituted C6-C30 aryloxy group, asubstituted or unsubstituted C2-C30 heterocyclic group, a substituted orunsubstituted C6-C30 condensed polycyclic group, a hydroxy group, acyano group, and a substituted or unsubstituted amino group, and,alternatively, two or more adjacent groups among R₁, R₂, R₃, R₁′, R₂′and R₃′ can be connected to each other to form a saturated orunsaturated carbocycle; each Ar is independently a substituted orunsubstituted C6-C30 aryl group or a substituted or unsubstituted C2-C30heteroaryl group; and Y is a halogen atom.
 3. The method of claim 2,wherein the reaction is carried out in the presence of Pd₂(dba)₃ wheredba is dibenzylideneacetone, sodium tert-butoxide, andtri(tert-butyl)phosphine at a temperature of 50 to 150° C.
 4. An organicelectroluminescent display device, comprising: a first electrode; asecond electrode; and an organic layer interposed between the firstelectrode and the second electrode, the organic layer comprising acompound represented by Formulae 5, 7 and 27:


5. The organic electroluminescent device of claim 4, wherein the organiclayer is a hole injection layer or a hole transport layer.
 6. Theorganic electroluminescent device of claim 4, wherein the organic layeris a single layer serving as both a hole injection layer and a holetransport layer.
 7. The organic electroluminescent device of claim 4,wherein the organic layer is an emitting layer.
 8. The organicelectroluminescent device of claim 7, wherein the emitting layer iscomposed of a phosphorescent or fluorescent material.
 9. The organicelectroluminescent device of claim 7, wherein the compound is used as afluorescent or phosphorescent host in the emitting layer.
 10. Theorganic electroluminescent device of claim 4, wherein the compound is acompound represented by Formula (5):


11. The organic electroluminescent device of claim 4, wherein thecompound is a compound represented by Formula (7):


12. The organic electroluminescent device of claim 4, wherein thecompound is a compound represented by Formula (27):


13. The compound of claim 1, wherein the compound is represented byformulae (5).
 14. The compound of claim 1, wherein the compound isrepresented by formulae (7).
 15. The compound of claim 1, wherein thecompound is represented by formulae (27).